Complete the following achievements to unlock Xbox Live Gamerscore points.

Achievement

How to unlock

All Ears ( 30 points )

Found 15 Audio Logs, alone or with another ODST.

Audiophile ( 75 points )

Found all Audio Logs, alone or with another ODST.

Be Like Marty ( 10 points )

In Firefight, finished a full round without killing a single enemy.

Boom, Headshot ( 5 points )

Got 10 automag headshot kills in any level.

Both Tubes ( 5 points )

Got 10 Rocket kills on Kizingo Boulevard.

Campaign Complete: Legendary ( 100 points )

Completed Legendary and unlocked the Dare character in Firefight.

Campaign Complete: Heroic ( 100 points )

Completed the Campaign on Heroic difficulty.

Campaign Complete: Normal ( 100 points )

Completed the Campaign on Normal difficulty.

Coastal Highway ( 50 points )

Completed Coastal Highway and unlocked the Last Exit Firefight mission.

Dark Times ( 5 points )

Killed 5 enemies while using VISR mode.

Data Hive ( 50 points )

Completed Data Hive and unlocked the Chasm Ten Firefight mission.

Dome Inspector ( 5 points )

Got 15 headshot kills on NMPD HQ.

Ewww, Sticky ( 5 points )

Got 5 sticky grenade kills in any level.

Firefight: Alpha Site ( 10 points )

Scored over 200,000 points in Firefight on Alpha Site.

Firefight: Chasm Ten ( 10 points )

Scored over 200,000 points in Firefight on Chasm Ten.

Firefight: Crater ( 10 points )

Scored over 200,000 points in Firefight on Crater.

Firefight: Last Exit ( 10 points )

Scored over 200,000 points in Firefight on Last Exit.

Firefight: Lost Platoon ( 10 points )

Scored over 200,000 points in Firefight on Lost Platoon.

Firefight: Rally Point ( 10 points )

Scored over 200,000 points in Firefight on Rally Point.

Firefight: Security Zone ( 10 points )

Scored over 200,000 points in Firefight on Security Zone.

Firefight: Windward ( 10 points )

Scored over 200,000 points in Firefight on Windward.

Good Samaritan ( 20 points )

Killed no Engineers in the city at night during entire campaign, alone or with another ODST.

Gumshoe ( 10 points )

Found the 3rd clue unravelling the mystery, alone or with another ODST.

Headcase ( 5 points )

Finished any level with at least one Skull activated.

Heal Up ( 5 points )

Found the first Medical Kiosk and healed yourself.

I Like Fire ( 5 points )

Killed 10 enemies with the Flamethrower on Data Hive.

Junior Detective ( 10 points )

Found the first clue unravelling the mystery.

Kikowani Station ( 30 points )

Completed Kikowani Station on Normal, Heroic or Legendary.

Kizingo Boulevard ( 30 points )

Completed Kizingo Blvd. and unlocked the Mickey character in Firefight.

Laser Blaster ( 5 points )

Got 10 Spartan Laser kills on ONI Alpha Site.

Listener ( 5 points )

Found the first Audio Log.

My Clothes! ( 5 points )

Plasma Pistol Overcharged and quickly killed 10 Brutes.

Naughty Naughty ( 5 points )

Killed 10 Engineers in the city at night, alone or with another ODST.

NMPD HQ ( 30 points )

Completed NMPD HQ and unlocked the Romeo character in Firefight.

ONI Alpha Site ( 30 points )

Completed ONI Alpha Site and unlocked the Alpha Site Firefight mission.

Pink and Deadly ( 5 points )

Got 10 Needler supercombine kills on any covenant.

Stunning! ( 5 points )

Stunned a vehicle with an overcharged plasma pistol and quickly killed the driver.

Super Sleuth ( 10 points )

Found the final clue unravelling the mystery, alone or with another ODST.

Tayari Plaza ( 30 points )

Completed Tayari Plaza and unlocked the Buck character in Firefight.

Tourist ( 5 points )

Accessed and downloaded the city map to your VISR.

Trading Down ( 5 points )

Traded weapons with a fellow character

Tuned In ( 15 points )

Found 3 Audio Logs, alone or with another ODST.

Uplift Reserve ( 30 points )

Completed Uplift Reserve and unlocked the Dutch character in Firefight.

Vidmaster Challenge: Classic ( 25 points )

Finished any level solo on Legendary, on LIVE, with no shots fired or grenades thrown.

Vidmaster Challenge: Deja vu ( 25 points )

Completed Highway on 4-player Legendary LIVE co-op, with Iron, and no Hog or Scorpion.

Vidmaster Challenge: Endure ( 25 points )

In Firefight, on any mission, passed the 4th Set on 4-player Heroic LIVE co-op.

Wraith Killer ( 5 points )

Killed all Wraiths in Uplift Reserve

Avatar Awards

Complete the indicated task to unlock the corresponding Avatar Award.

Award

How to unlock

ODST Armor

Unlock Good Samaritan achievement.

ODST Helmet

Unlock Campaign Complete achievement.

ODST Hoodie

Unlock Dark Times achievement.

ODST Shirt

Unlock Tourist achievement.

Recon Helmet

Unlock the Vidmaster Challenge: Endure achievement.

Buck & the Monkey

First of all, you need patience. If you don't, then just stop reading. You need to complete Coastal Highway. Wait until the credits are over (which will take a while). When the epilouge starts, start holding RS to the left. Keep holding it. When it should show the engineer lighting Sgt. Johnson's cigar, it will pan left and show Gunny "playing" with one of the monkeys from the monkey easter egg in Halo 3 Serria 117.

Data Hive: 30th audio file

The 30th (last) audio file for Sadie's Story is not in the "Mombasa Streets" but rather in the "Data Hive" level (also played by the Rookie). However, it will be in a locked area until you find the 29 audio files in the Mombasa Streets. Once you find those files, play the mission "Data Hive" until you reach the hole to get to Sub-station 9. If you found the previous files, instead of the Superintentation closing off the hole so your cop teammate cannot get through (and ultimately get killed by Drones), he will climb down the hole with you. Continue playing until the cop says something similar to "Wait here, I need to go check something." Follow him and he will reveal his true purpose for coming here and will fight you. During or after the fight, you can scan the phone on the wall next to the dead body to find the 30th audio file. Note, finding the audio file will slightly alter the scene, specifically the part where DARE and the Rookie finds Vergil. Instead of DARE telling the Rookie not to shoot, the Rookie will tell DARE not to fire and instead whistle for Vergil to come out.

Defeating Engineers

In order to take down an Engineer quickly, use the Covenant pistol. Fully charge it to take down Engineers with one shot. This applies to both Firefight, and Campaign modes.

Easy "Both Tubes" achievement

Before boarding the Scorpion, hand your rocket launcher to any Marine riding on the tank. Note: For more mayhem, pick up the other rocket launcher from behind the tank and hand that off as well. Any kill the Marine makes counts toward the achievement. The Marine has unlimited ammunition, and will make getting the achievement much easier.

Easy "Vidmaster Challenge: Classic" achievement

In Uplift Reserve, grab the Warthog at the beginning and load up with Marines. Shots fired from the Marines do not count, and you cannot use the e-brake or horn. Just fly through the level.

This achievement requires you to finish any mission under the Legendary difficulty setting with no shots fired. E-braking or honking the horn with the Warthog counts against you. Most players just pile a group of Marines into a Warthog and let them do all the shooting. The following method works slightly faster, and is a bit easier. When you get around the first corner from the starting point, there is a small battle going on with a Wraith and a few smaller Covenant vehicles firing on a squad of UNSC forces. Hijack a Ghost from that area and boost all the way to the end of the level. The boost on the Ghost does not count as firing a shot. If your Ghost is getting trashed, there is a new one on the other end of the bridge you cross as the Space Elevator collapses. Also, you can climb the hill just after this location using the boost feature, instead of going along the path and getting shot at by the two Shade emplacements.

Easy "Vidmaster Challenge: Déjà Vu" achievement

Play under the Legendary difficulty setting with the Iron Skull on. Two Mongooses you can use as transport will appear inside the first open tunnel you can walk into after starting on the highway. Also accompanying the Mongooses are four rocket launchers with 999 shots. Take each piece of highway slowly and make sure to cover DARE when she gets overwhelmed.

Energy sword handle markings

Go to forge. Go to the map sandbox. Spawn a sniper and an energy sword. Pick up the sniper and the energy sword on the ground. Use the sniper and zoom in all the way on the handle. There will be some weird Covenant symbols. If the sniper doesn't work, try zooming in when you're in monitor mode.

Epilogue video

Successfully complete the game and do not interrupt the credits. The Epilogue video will begin playing after the credits end.

Finding secret doors

While using VISR mode as the Rookie, look out for secret doorways. Accessible doors will turn the amber outlines of objects in front of them blue. This is easiest to see on your weapon. Watch for them because many of these doors hide data terminals.

Firefight mode: Characters

Complete the indicated task to unlock the corresponding character for Firefight mode.

Buck: Complete Tayari Plaza under the Normal or higher difficulty.
Dare: Complete the Campaign under the Legendary difficulty.
Dutch: Complete Uplift Reserve under the Normal or higher difficulty.
Mickey: Complete Kizingo Boulevard under the Normal or higher difficulty.
Romeo Character: Complete NMPD HQ under the Normal or higher difficulty.

In the "Prepare To Drop" mission , when the Carrier jumps to Slipspace Rupture, closely look at the right of the Carrier. You will see the Amber Clad of Commander Keyes getting into the Slipspace Rupture along with the Carrier. In Halo 2, at the end the "Metropolis" mission cinematic, you will see the Amber Clad of Commander Miranda Keyes to the right of the Carrier entering the Slipspace Rupture along with the Carrier. This is a true reference for the following reasons. In Halo 3: ODST, you are in New Mombasa and the Carrier is floating next to the space elevator. In Halo 2 you are also in New Mombasa, and at the beginning of the level on the bridge, you can see the space elevator and the Carrier floating next to it. In both Halo 3: ODST and Halo 2, when the Carrier jumps there will be a big EMP wave.

Kizingo Boulevard

You need to have completed the game for this to work. Start on level Kizingo Boulevard. Now, remember the the night mission where you go up to the busted gauss turret? Go up there. You can't use the turret but instead of being just an assault rifle, there will be two or three rocket launchers and a sniper rifle.

Kizingo Boulevard: Ghost

When you find the Gauss rifle near the end of the level, do not kill all of the Ghosts that get dropped. Grab one of them out from under the Brute. Kill the Brute, then kill the Wraith. Ride the Ghost up to the barrier by Dutch. Give Dutch a rocket launcher if you have one, and he will help decimate the incoming enemies. If you were fortunate, you should have obtained a plasma cannon (most efficient, but this trick will work with any weapon) earlier in the level behind the spare tank, before you go thru the first door. It is located back in a side road off the courtyard with the multiple turrets. Use the plasma cannon with a melee attack (B) to walk/push the Ghost through the invisible barrier. This will make the end of the level quite a bit easier. You can get multiple kills by running over groups of Covenant with the LT boost on the Ghost. When everything else is mostly cleared, you can stun the Wraith with an overcharged plasma pistol, and then proceed to defeat it in any desired manner.

Lost Platoon: Safe location from Covenant

Steal a chopper and ride it up the mountains. There will be a crack where you cannot see anyone and where they also cannot see you. You cannot shoot them, but they also cannot shot you. This is useful if you have an idle player in order to keep them safe.

Mombasa Streets: Audio Logs

The units you can get Audio Logs from in the Mombasa Streets level all have a picture of the Superintendent on them (the green smiley with white eyes and no mouth).

ODSTs compared to Spartans

Spartans are humans who are like machines (as noted by Bungie, "Like a Spartan, you are half human, half machine"). Orbital Drop Shock Troopers (ODSTs) are like ordinary Marines, only they are highly trained, but they are not like Spartans. A mistake made by Bungie makes the player slightly like Spartans for the following reasons: during game play you are as tall as a Spartan when you are standing next to an ODST squad mate; you can wield a Gravity Hammer, which actually the only ones known to wield them are Spartans, Elites, and Brutes, not ODSTs; and you can melee Brutes to death, while only Spartans can do that. The melee attacks performed by people with lower ranks than Spartans do not affect Brutes at all.

Recon Armor

Unlock the seven "Vidmaster challenge" achievements in both Halo 3 and Halo 3: ODST. Then, flip the switch on your Bungie.net service record (look for the "Road to Recon" under your trophy shot). Note: You will need a valid and linked Bungie.net account to complete the required steps.

Uplift Reserve: Strange Marine dialogue

Play through the mission as usual until you go up towards a hill to meet a large purple platform, with a good number Of covenant around and in it. Drive or walk around the left side of it to meet a dipped down curve with a few Marines taking cover in it. Look for a Warthog. Behind it, look for a Marine talking to another wounded Marine on the ground. Turn up the volume so you can hear the conversation clearly. It sounds like the wounded Marine is talking about being animals in a cage, and the Covenant as if they were the predators. The conversation soon stops after awhile.